It sometimes occurs that electrical cable and/or tubing bundles are required to provide electrical and/or material transfer or pneumatic signals between two locations in such a manner that the cable and/or tubing bundle does not act as a conduit for the transfer of the vaporous or gaseous environment of one location to the other. Of particular importance are situations where one location is desigated as a non-hazardous location and the other location is designated as hazardous such as, for example, where one location is an electrical control room and the other is a location having an explosive vaporous or gaseous environment. Under such circumstances, it is vital that the cable and/or tubing bundle does not act as a conduit for transfer of the explosive gas or vapor to the electrical control location so as to prevent the possibility of its ignition from an electrical spark or other source of ignition.
Authorized means for the prevention of such gas flow transfer occurrences is established under Article 501 of the National Electrical Code of which Articles 501-b and -e respectively cover conduit and electrical cable seal connections between a Class 1 Division 2 hazardous location and a non-hazardous location.
The problem of preventing gaseous flow through electrical cable and/or tubing bundles has commonly been solved in the past by filling the open spaces or interstices between the electrical wires and/or tubes within a bundle with a sealing compound approved for the purpose or alternatively to use approved sealing fittings at the ends of the cable and/or bundle. Two of the advantages of sealing the end of an electrical cable and/or tubing bundle versus filling them with a sealing compound are that the complications of filling during the manufacturing process are eliminated and the cable and/or bundle is necessarily considerably lighter in the absence of such sealing compound throughout the entire length of the electrical cable or tubing bundle.
One of the methods used in the past to seal the ends of an electrical cable is by the use of heat shrinkable and cap break-outs such as disclosed in U.S. Pat. No. 3,949,110. Although such break-outs may be used to advantage they have the disadvantages of: (1) having an enlarged outside dimension due to the bulkiness of the exterior shrunken covering extending about each conductor from the end of the cap; (2) require that the covering about each conductor or groups of conductors be shrunken individually by the use of heat; and (3) are unable to provide the number of outlets per unit of cross-sectional area associated with the sleeve of the present invention.
Another method that might be used to seal the ends of an electrical cable is the combination of a heat recoverable member and a fusible insert such as respectively disclosed in U.S. Pat. Nos. 3,396,460 and 4,206,786. The method however requires the use of a separate fusible insert that melts to fill the air spaces and voids between conductors when the heat recoverable member is caused to shrink by the application of heat and does not offer a compact one-piece recoverable sleeve having internal walls separating the conductors and providing both strength and support thereto.
Another method for sealing interconnections between electrical wire ends is disclosed in U.S. Pat. No. 3,525,799 where a heat recoverable sleeve is used in conjunction with an internal polymeric material about the conductors such that, when the sleeve is shrunken under heat, the polymeric or solid material melts and seals the area between the sleeve and the conductor. The disadvantages of such method are the expense and inconvenience of having to inventory and handle a multicomponent system and that such method would apt to be extremely complex when a plurality of electrical conductors and/or tubes are involved.
A method of aligning a plurality of pins within a heat recoverable sleeve for respectively connecting to each of a plurality of electrical conductors is disclosed in U.S. Pat. No. 4,022,519. Although the pins are aligned by use of molded blocks contained within the sleeve, the blocks do not have the ability to shrink about the pins during the process of shrinking the sleeve and thus may not provide a suitable barrier to the flow of gas.